Abstract
In a former paper 1 it was shown that when the marine alga, Valonia, was placed in solutions of methylene blue dissolved in sea water at pH's 5.8 and 9.0, the dye penetrating into the sap was methylene blue itself and not some lower homolog, such as trimethyl thionin, formed by the oxidation of methylene blue in the outside solution. The identification of the dye was made by means of the spectrophotometer.
In order to test this conclusion still further, another set of experiments was made using the fresh water alga, Nitella. The method was similar to that used in the experiments with Valonia. The same sample of dye was also used. All necessary precautions were taken during extraction to keep the sap from becoming contaminated by dye from the rest of the cell. The plants were also tested for injury by transferring samples from the experimental solutions to tap water. These were found to be alive (green and turgid) 2 months after experimentation, when they were discarded.
In the experiments herewith reported selected Nitella cells of the same size were placed in solutions of methylene blue for 2 hours at 25° C., after which the sap was extracted, placed in a hollow ground slide with a flat-bottomed depression, covered by a cover slip, and spectrophotometric measurements made.
It was found that the dye penetrating into the sap had a maximum absorption at 660 mμ and a secondary maximum at 610 mμ. These are the absorption maxima for methylene blue. It is therefore concluded that methylene blue penetrates Nitella sap as such. This corroborates the previous results obtained by the writer with Valonia.
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